While unilateral electroconvulsive therapy (U-ECT) is generally considered to induce negligible disturbances of memory as compared with bilateral bitemporal ECT, its relative antidepressant efficacy has been questioned. The aim of the present study was to compare, in a double-blind design, clinicians' ratings of global clinical impression of the antidepressant efficacy of the two treatment modalities. The treatment technique included avoidance of benzodiazepines, prolonged hyperventilation with oxygen, intermittent unidirectional pulses distributed in a long pulse train, permitting individualized and relatively high doses of electrical charge at each treatment occasion, and non-dominant long-distance (12-13 cm) parietotemporal (d'Elia) electrode placement in the U-ECT group. The results indicated no therapeutic advantage for either treatment modality, which was also in accordance with the symptom ratings by an independent nonblinded rater. The findings encourage the continued use of nondominant long-distance parietotemporal ECT with a treatment technique that induces fully generalized seizures as the modality of choice in the convulsive treatment of depression.